INCB16562 is an orally active and selective inhibitor against JAK1/2 markedly selective over JAK3. INCB16562 potently inhibits interleukin-6 ( IL-6 )-induced phosphorylation of STAT3. Additionally, INCB16562 inhibits the proliferation and survival of myeloma cells dependent on IL-6 for growth, as well as the IL-6–induced growth of primary bone marrow-derived plasma cells. INCB16562 antagonizes the growth of myeloma xenografts in mice with antitumor activity. INCB16562 is promising for research of multiple myeloma.